This project features the integration of advanced photonic technology and microfluidics to attack a major unmet challenge in cell biomechanics. The cellular microenvironment critically regulates cellular function by providing a complex mixture of biochemical and biophysical stimuli. Among the components of the cell-microenvironment interaction, the role of biomechanical factors is recognized to be crucial. In recent years, tremendous progress has been achieved in developing single-cell tools for mechanical stimulation and force response. One area of needed improvement is the non-invasive measurement of intracellular elasticity. Elasticity mediates the transmission of forces inside the cell and the deformation experienced by cell regions under an applied force. However, current technology for cell/ECM elasticity measurements is limited to point-sample analysis or requires contact. These are important limitations since cells are heterogeneous, alter their properties upon mechanical perturbation, and need to be studied in 3D microenvironments. This project will develop an all-optical approach to this unmet need. Brillouin cellular microscopy can map the intracellular elasticity at high resolution, non-perturbatively, without contact in 3D cultures. Brillouin information on cell elasticity will be co-located with fluorescent-based detection of cytoskeletal components and intracellular mechanotransduction. Integration with microfluidic platforms will enable tight control of microenvironment conditions. After instrument validation, I will focus on breast cancer cell migration. Based on preliminary data and literature evidence, I formulated and will test the hypothesis that intracellular elasticity mediates migratio, namely that optimal cell modulus and elasticity polarization are mechanical requirements of the migration machinery and can be used to explain the enhanced motility exhibited by metastatic cells compared to their non-cancerous counterparts. Beyond the cell migration studies, the novel instrumental platform developed and validated during this award, will be broadly applicable as it provides unique quantitative metrics to relate cell- microenvironment mechanical interaction to cell behavior. This K25 award would enable the candidate's transition to research in cellular biomechanics and mechanobiology by complementing his demonstrated expertise in optical technology development with the necessary training in cell biology, microfluidics and ethical research conduct through formal coursework, interaction with mentors and hands-on laboratory training.